Experimental and numerical investigation of the water-entry and water-exit of a circular cylinder

The water entry of a body is a very important topic in naval hydrodynamic. This phenomenon plays an important role both for offshore structures and for vessels. High forward speed of the vessel and rough head sea states usually lead to the most severe water entry events. In such circumstances, the wave-body interactions may result in pronounced motions of the vessel with largest amplitudes at the bow region. In this area, the probability of water entry is the largest, i.e. portions of the hull can more easily touch the sea surface at high relative velocity. The water-entry phenomenon is intrinsically a transient phase. Its beginning can be characterized by highly localized, both in space and in time, loads on the vessel, influencing both the local structural safety of the ship and the global loads acting on the ship itself.Here an experimental and numerical analysis is performed for a circular cylinder either freely falling on or exiting the water. From the experimental point of view, a detailed measurement of the velocity field and of the local loads around the cylinder is carried out.